Armature-core for dynamo-electric machines



(No Model.)

E. THOMSON. ARMATURE CORE FCR DYNAMC ELECTRIC MACHINES.

No. 463,671. Patented Nov. 24, 1891.

UNITED STATES PATENT OFFICE.

ELIHU THOMSON, OF LYNN, MASSACHUSETTS, ASSIGNOR TO TIIE THOMSON- HOUSTONELECTRIC COMPANY, OF CONNECTICUT.

ARMATURE-CORE FOR DYNAMO-ELECTRIC MACHINES.

SPECIFICATION forming part of Letters Patent No. 463,671, dated November24, 1891.

Application filed August 5, 1889. Serial No. 319,829. (No model.)

To all whom t may concern.:

Be it known lthat I, ELIHU THOMSON, a citizen of the United States, anda resident of Lynn, in the county of Essex and State of Massachusetts,have invented a certain new and useful Improved Armature-Core forDynamo-Electric Machines, of which the following is a specification.

My invention relates to the construction of cores for electric-inductionapparatus subject to rapidly-varyin g magnetic polarization, and isdesigned more particularly for the cores of dynamo-electric generatorsand motors.

The invention consists, essentially, of a core built up from plates ofthin sheet-iron or groups of sheet-iron plates consisting of theordinary sheet-iron of commerce having the thin insulating scale orcoating produced in the operation of manufacture, said sheets beingseparated from one another by the said plates of tin, zinc, or other non-magnetic metal. In this structure the thin coating or scale upon thesheet-iron disks or plates forms an electrical insulation, while theplates or washers of tin, zinc', or other non-magnetic metal form amagnetic insulation.

In the accompanying drawings, Figure l shows in plan the ordinaryconstruction of a disk armature, the central portion being A are madefrom sheet-iron of small gage.

broken away. Fig. 2 shows in section a portion of an armature-coreconstructed in accordance with my invention. Figs?) and a arerespectively a side elevation and edge view of a modified construction.Fig. 5 shows in edge view a further modication. Figs. 6 and 7 show inside elevation and section another modification.

In Fig. 2, D are disks or plates ot' thin sheetiron built u p laterally.This sheet-iron is the ordinary sheet-iron of commerce, which, as iswell known, during the process of manufacture acquires a thin scale orcoating, which is to some extent an electrical insulation. The platesare shown magnified in the drawings as to their thickness. In practicethey tween groups of these pieces ot' sheet-iron are placed sheets ofzinc Z, the whole being firmly held together by bolts B, surrounded byinsulation I. It is not necessary that the sheets of zinc should fill'the entire space between the iron disks. As shown in Fig. 3, the zincmay be cut into washers Z of suitable size and strung upon the bolts B,Fig. 4f, and between the disks of sheet-iron; or, again, the

Zinc sheet Z may, as in Figs. G and 7, be circular in form, with itsinterior portion removed, and the bolts passed therethrough. Sometimes Iconstruct the core of alternate plates of sheet-iron and Zinc, asindicated in Fig. 5. 6o

The thin scale or tllm before referred to upon the sheet-iron forms anadherent layer of a material which'is an insulator of electricity andconstitutes the natural scale or film ot' iron oxide whichis produced inanneal- 65 ing or heating the sheet-iron in the ordinary process ofmanufacturing the same. As this iilm forms a hard adherent coating,itmay be rmly compressed without damage when the plates of sheet-iron andnon-magnetic metal 7o are clamped by bolts. This lm constitutes aprotection against the formation of local electric currents parallel tothe armature-shaft.

The chief cause of heating of armatures is not so much due to currentsproduced paralof the disks, according to the character of the 8o ironemployed, and in other cases the result of the disks moving in anintense magnetic field and the consequent crowding of the lines offorce.

By the employment of thin plates of zinc or other non-magnetic metal asan insulator for this magnetic leakage the heating effects mentioned arelargely overcome. The disks of sheet-iron and zinc can be boltedtogether firmly, and there is thus formed a solid struct- 9o ure, whichis not liable to become loose or shaky, as is the case when paper orother vegetable material is employed as au electrical or magneticinsulator between the plates.

I am aware that it has heretofore been pro- 9 5 posed to build up thecores of armatures or other electrical apparatus from thin plates ofiron secured together, but magnetically insulated from one another byinterposed instilating material, such as asbestus, hard rubroo ber,wood, paper, or other similar substance, which, besides beingnon-magnetic in character, is an electrical insulator, and will preventthe formation ot the electric currents parallel to the armature-shaft. Iam also aware that it has been before proposed to use tin or othernon-magnetic metal as the magnetic insulator; but in such cases it hasordinarily been proposed to use the tin or zinc as a thin coating` orplating upon the sheet of iron. This renders necessary a specialpreparation of the iron plates to be used in building up the core, andbesides may not in all cases form an etlicient magnetic insulator.Another 0bjection to this construction of the core is that in order toform a film or plating of the metal upon the iron it is necessary thatthere should be no scale or insulating film between the film ofnon-magnetic metal and the iron itself, so that it becomes necessary toprovide other means for electrically insulating the plates from oneanother.

lVhat I claim as my invention isl. An iron core for electricalapparatus,built up from plates of sheet-iron liavinga thin adherentscale or coating of hard insulating substance formed naturally in theprocess of manufacturing sheet-iro11, as described, and thin interposeddistinct separating-plates of zinc, tin, or other non-magnetic metal,all secured together as a solid structure by any suitable means.

2. An iron laminated core for electrical apparatus, composed ot a seriesof plates of sheet-iron, each having a thin hard adherent coating of aninsulating natureand mechanically separated from other plates byinterposed metal plates or Washers of some nonmagnetic metal, the Wholebeing secured together by bolts to form a solid structure.

Signed at Lynn, in the county of Essex and tate of Massachusetts, thislst day of August, A. D. 1889.

ELIHU THOMSON.

Witnesses:

JOHN W. GIBBoNnY, A. L. ROHRER.

